Currently, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, lithium secondary batteries, and the like are used as commercial secondary batteries. Among them, lithium secondary batteries have little to no memory effect in comparison with nickel-based secondary batteries, and thus lithium secondary batteries are gaining a lot of attention for their advantages of free charging or discharging, low self-discharging, and high energy density.
A lithium secondary battery generally uses lithium oxide and carbonaceous material as a positive electrode active material and negative electrode active material, respectively. The lithium secondary battery includes an electrode assembly in which a positive electrode plate and a negative electrode plate respectively coated with the positive electrode active material and the negative electrode active material are disposed with a separator being interposed between them, and an exterior, namely a battery case, which seals and accommodates the electrode assembly together with an electrolyte.
Generally, a lithium secondary battery may be classified into a can-type secondary battery where the electrode assembly is included in a metal can and a pouch-type battery where the electrode assembly is included in a pouch of an aluminum laminate sheet, depending on the shape of the exterior.
Recently, secondary batteries are widely used not only for small-sized devices such as cellular phones but also middle-sized or large-sized devices such as vehicles and power storages. When being used for middle-sized or large-sized devices, a great number of secondary batteries are electrically connected to enhance capacity and output. In particular, in middle-sized or large-sized devices, pouch-type secondary batteries are frequently used since they can be easily stacked and have light weight.
If a secondary battery is heated over a proper temperature, the performance of the secondary battery may deteriorate, and in severe cases, the secondary battery may be exploded or fired. In particular, when a plurality of pouch-type secondary batteries are stacked to configure a battery module, the heat emitted from the plurality of secondary batteries in a narrow space is accumulated, which may raise the temperature of the battery module rapidly and severely. Further, if the battery module is included in a battery pack for a vehicle, the battery module may be frequently exposed to direct sunlight and may also be placed in a high-temperature condition, for example in summer or in a desert.
Therefore, when a battery module is configured using a plurality of secondary batteries, it is very important to ensure stable and effective cooling performance. However, since the battery module is consistently demanded to have a small design, ensure rigidity and enhance capacity, it is substantially required to develop a battery module which may enhance cooling performance while satisfying various demands as above.